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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

36277 results found.

  1. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  2. GRB 260318A: GECAM-B observation
  3. Fermi GRB 260318A: Global MASTER-Net observations report
  4. GRB 260318A: Fermi GBM Final Real-time Localization
  5. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  6. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  7. GRB 260310A / AT 2026fgk: radio detection with the VLA
  8. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  9. GRB 260310A / AT2026fgk: LCO optical observations
  10. GRB 260317A: Fermi GBM Final Localization
  11. GRB 260316B: GECAM-B observation
  12. GRB 260316B: SVOM/GRM observation
  13. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  14. GRB 260316B: AstroSat CZTI detection
  15. GRB 260316B: Fermi GBM Final Real-time Localization
  16. EP260316a: optical upper limit with Kinder observations
  17. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  18. GRB 260314A: Glowbug gamma-ray detection
  19. EP260314a: optical upper limit with Kinder observations
  20. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  21. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  22. GRB 260310A / AT 2026fgk: iTelescope optical observations
  23. GRID detection of GRB 260312B
  24. EP260314a: BOOTES-6/DPR optical upper limits at early times
  25. GRB 260314A: GECAM-B observation of a burst
  26. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  27. GRB 260310A / AT2026fgk: SAO RAS optical observations
  28. GRB 260310A/AT2026fgk: radio detection at 15GHz
  29. GRB 260310A / AT2026fgk: TNG NIR detection
  30. GRB 260310A / AT2026fgk: OASDG optical observations
  31. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  32. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  33. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  34. Fermi GRB 260314A: Global MASTER-Net observations report
  35. Fermi GRB 260313A: Global MASTER-Net observations report
  36. GRB 260314A: Fermi GBM Final Real-time Localization
  37. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  38. GRB 260313A: A Correction to the Fermi GBM Final Localization
  39. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  40. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  41. GRB 260310B: Insight-HXMT/HE detection
  42. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  43. GRB 260310A: NOT optical polarimetry
  44. GRB 260312B: AstroSat CZTI detection
  45. Swift BAT trigger 1500295: A solar flare
  46. GRB 260313A: Fermi GBM Final Real-time Localization
  47. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  48. Swift BAT trigger 1500287: A solar flare
  49. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  50. GRB 260308A: Insight-HXMT/HE detection
  51. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  52. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  53. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  54. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  55. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  56. GRB260310A / AT2026fgk: P200 Spectroscopy
  57. GRB 260312B: Glowbug gamma-ray detection
  58. GRB 260310A: Fermi GBM Observation
  59. GRB 260310A: potential optical counterpart
  60. Fermi GRB 260312B: Global MASTER-Net observations report
  61. Fermi GRB 260311B: Global MASTER-Net observations report
  62. Swift BAT trigger 1500148: A solar flare
  63. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  64. GRB 260312B: Fermi GBM Final Real-time Localization
  65. GRB 260310B: GECAM-B observation of a burst
  66. Retraction of GCN 43965: GRB is actually solar flare
  67. GRB 260312A: Swift detection of a burst
  68. GRB 260311B: Fermi GBM Final Real-time Localization
  69. GRB 260131A/B: radio detection with the VLA
  70. GRB260307A: GECAM-B observation of a burst
  71. GRB 260308A: SVOM/GRM observation of a short GRB
  72. EP260306a: Mondy optical upper limit
  73. GRB 260310A: AstroSat CZTI detection of a long burst
  74. GRB 260311A: Fermi GBM Final Real-time Localization
  75. Fermi GRB 260310B: Global MASTER-Net observations report
  76. GRB 260310B: Fermi GBM Final Real-time Localization
  77. Fermi GRB 260310A: Global MASTER-Net observations report
  78. GRB 260307B: SVOM/ECLAIRs refined analysis
  79. GRB 260208A: radio detection with the VLA
  80. GRB 260310A: Fermi GBM Final Real-time Localization
  81. GRB 260307A: Glowbug gamma-ray detection
  82. GRB 260308A: Fermi GBM Final Real-time Localization
  83. Fermi GBM Sub-Threshold Detection of GRB 260307B
  84. GRB 260307B: Mephisto optical upper limits
  85. GRB 260307B: possible NOT optical counterpart
  86. GRB 260307B: SVOM/VT upper limit with X band data analysis
  87. Fermi GRB 260307A: Global MASTER-Net observations report
  88. GRB 260307B: SVOM/VT optical candidate
  89. GRB 260307B: SVOM/C-GFT upper limit
  90. GRB 260307B: SVOM detection of a burst
  91. GRB 260307A: Fermi GBM Final Localization
  92. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  93. GRB 260207A: TESS Detection and Possible VLA Counterpart
  94. EP260302a: Optical afterglow rebrightening
  95. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  96. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
  97. GRB 260303A: 1.3m DFOT optical upper limit
  98. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  99. GRB 260303A: SVOM/ECLAIRs refined analysis
  100. Fermi GRB 260305A: Global MASTER-Net observations report

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